1. Technical Field
The present invention relates to a process for producing 3-chloro-N-(3-chloro-5-trifluoromethyl-2-pyridyl)-α,α,α-trifluoro-2,6-dinitro-p-toluidine as an active ingredient of pesticides (common name: fluazinam).
2. Background Art
U.S. Pat. No. 4,331,670 (Patent Document 1) discloses a process for producing 3-chloro-N-(3-chloro-5-trifluoromethyl-2-pyridyl)-α,α,α-trifluoro-2,6-dinitro-p-toluidine which comprises reacting 2-amino-3-chloro-5-trifluoromethylpyridine and 2,4-dichloro-3,5-dinitrobenzotrifluoride in the presence of a base and a solvent and discloses alkali metal hydroxides, carbonates and hydrides or alkaline earth metal hydroxides and carbonates as examples of the base and aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, tetrahydrofuran (THF), sulfolane and dioxane as examples of the solvent.
WO 2007/060662 (Patent Document 2) discloses the use of methyl isobutyl ketone (MIBK) as the solvent in the above-mentioned process disclosed in U.S. Pat. No. 4,331,670 (Patent Document 1). Patent Document 2 discloses that a higher yield is attained when the presence of water, which is hardly miscible with MIBK, in the reaction is minimized to decrease the hydrolysis by-product and that the presence of a high concentration of water resulting from the reaction or attributed to the reagents increases the hydrolysis by-product and thereby decreases the yield. Patent Document 2 also discloses that the ratio of the solvent to the reactant should be larger than about 10% w/v and that the solvent is preferably pure MIBK (for example, with a purity of about 98%) or recycled MIBK with a water content of less than 2%, and that in the production of fluazinam as the desired product described in Example 2, the reaction was carried out by adding solid KOH (3.5 mol eq.) to a mixture of 2-amino-3-chloro-5-trifluoromethylpyridine, 2,4-dichloro-3,5-dinitrobenzotrifluoride and a MIBK azeotrope containing 1.6% water.    Patent Document 1: U.S. Pat. No. 4,331,670    Patent Document 2: WO 2007/060662